Amazon insists that it doesn't do differential pricing, but on October 18 a high-profile tech blogger went ballistic because the E-tail giant apparently did just that. Tim Bray, who also happens to be a Google engineer, fumed that amazon.com had a $9.48 price on an e-book he wanted, but when he logged in to buy it, the price immediately jumped by more than $5—to $15.17. "Maybe there's an explanation," Bray wrote. "I don't care what it is, it's not good enough and it's not reasonable and I'm not paying that price and maybe you shouldn't be either." Whew!

The likely problem: Bray, a Canadian, was visiting Amazon's U.S. site, where Amazon sets its own e-book prices under terms of a price-fixing settlement. Once Bray logged in, Amazon spotted him as Canadian and gave him Amazon Canada's price, which is set by the publisher. (The fact that publishers also run their own sale prices may be why e-book prices also seemed to drop for Bray as soon as he bought books.) But it's still aggravating to customers. And that cross-border quirk means Amazon does differential pricing after all—no matter how much it tries not to.